There are two ways to calculate mobile phones. 1. Pay a monthly rent of 22 yuan per month, and then charge 0.2 yuan per minute. 2. No monthly rent, 0.4 yuan per minute Q: if you talk for 80 minutes a month, which is cheaper?

2 * 80 = 38
The second one is 0.4 * 80 = 32
So the second is cost-effective
Hope to adopt

As shown in the figure, in isosceles ladder ABCD, AD / / BC, m and B are the midpoint of AD and BC respectively, e and F are the midpoint of BM and cm respectively
(1) Verification: the quadrilateral menf is a diamond. (2) if the quadrilateral menf is a square, please explore the relationship between the height of the isosceles trapezoid ABCD and the number of BC at the bottom, and explain your conclusion

(1) Because trapezoid ABCD is isosceles trapezoid, angle a = angle D, am = DM, ab = DC, so triangle ABM is congruent DCM, so BM = cm. Because e, N, f are the midpoint of BM, BC, cm respectively, so en = cm / 2 = FM, FN = BM / 2 = em, so en = FN = EM = FM, that is, quadrilateral menf is diamond

The volume of a wood block is 200cm to the third power, and the density is 0.8 × 10 to the third power, kggm to the third power. After immersing it in the water and letting it go, why can't the wood block be suspended in the water? When the wood block finally floats on the water, how much support does the bottom of the container have for it?

Taxi fare can be calculated by the formula y = P + QX. The known starting price is 3km
1. It is known that the taxi fare is 20 yuan when the journey is 8 km, and 24 yuan when the journey is 10 km. Find the value of p.q. (solve with binary linear equations)
2. It costs 16 yuan for someone to get to the destination by taxi. Q: how many kilometers is his journey?

Taxi fare can be calculated by the formula y = P + QX. The known starting price is 3km
1. It is known that the taxi fare is 20 yuan when the journey is 8 km, and 24 yuan when the journey is 10 km. Find the value of p.q. (solve with binary linear equations)
20=p+8q
24=p+10q
The solution is: q = 2, P = 4
2. It costs 16 yuan for someone to get to the destination by taxi. Q: how many kilometers is his journey?
y=4+2x
16=4+2x
x=6km
That's six kilometers

There is a shadow ellipse (like a leaf) in the middle of a square. Two points are on the two corners of the square. The side length of the square is 40cm. Calculate the shadow area and perimeter!

The circumference is equal to 1 / 2 of the circumference of a circle with a radius of 40
Namely: 2 π R / 2 = π r = 3.14 * 40 = 125.6
The area is equal to two quarter circles, that is, the area of a semicircle minus the area of a square
That is: 1 / 2 π R & # 178; - 40 * 40 = 912

We know that a = 3 1 / 3 times, B = 4 1 / 4 times, C = 6 1 / 6 times, try to compare the size relationship of ABC

12 times of a = 4 times of 3 = 81
12 times of B = 3 times of 4 = 64
12 times of C = 2 times of 6 = 36
∴a>b>c

An application problem of quadratic function in junior three mathematics,
A shopping mall sells a bag with a purchase price of 30 yuan at 40 yuan, with an average of 200 bags sold per month. The survey shows that if the selling price exceeds 40 yuan but does not exceed 60 yuan, the sales volume of this kind of bag will be reduced by 5 for every 1 yuan increase in the selling price. If the selling price exceeds 60 yuan, and if the price increases again, there will be no 1 yuan less time to buy each month. Suppose the selling price of each bag is x yuan, and the monthly sales volume is y pieces
【1】 Find the functional relationship between Y and X and write the value range of the independent variable x directly
【2】 Suppose that the monthly sales profit of the schoolbag is w yuan, please write the functional relationship between W and X directly
【3】 When the selling price of each schoolbag is set at RMB, the maximum profit can be obtained every month,
Pay attention to the third line, that is, for every 1 yuan increase, buy 10 pieces less per month

(1) When the selling price of 4060 is 60, the sales volume will decrease by 5 * (60-40). When the selling price exceeds 60, the sales volume will decrease by 10 (X-60). Y = 200-5 * (60-40) - 10 (X-60) = 200-100-10x + 600 = 700-10x (2) when 4060, w = (X-30) * (700-10x) = - 10x ^ 2 + 1000x-21000 (3) when 4060, w = (X-30) * (700 -

Cut a piece of paper with a side length of 10 cm into the largest circle. What percentage of the area of the circle is that of the square?

The area of the circle: S = π R2 = 3.14 × (10 △ 2) 2 = 78.5 (square centimeter); the area of the square: S = A2 = 10 × 10 = 100 (square centimeter); 78.5 △ 100 = 78.5%; answer: the area of the circle is 78.5% of the area of the square

If the sum of the square of half x + X + 1 and a is x, then a is equal to X____ .

If the sum of (1 / 2) x & # 178; + X + 1 and a is x, then a is equal to?
(1 / 2) x & # 178; + X + 1 + a = x, that is, (1 / 2) x & # 178; + 1 + a = 0, X & # 178; = - 2 (1 + a), x = ± √ [- 2 (1 + A)], thus, a ≤ - 1

Application problem: the process of solving the problem should be written in detail
For a project, it takes 20 days for Party A and Party B to do it alone, and 15 days for Party C to do it alone. Now three people work together. During this period, Party A goes out to study for two days, and Party C asks for leave for one day. How many days did it actually take to complete the project?

Let's take this project as an integer 1 and calculate it. Let's say: it took X days. (X-2) / 20 + X / 20 + (x-1) / 15 = 1 and multiply both sides by 60 to get: 3x-6 + 3x + 4x-4 = 60, 10x = 70, x = 7 days; check: 5 / 20 + 7 / 20 + 6 / 15 = 15 / 60 + 21 / 60 + 24 / 60 = 60 / 60 = 1

There are two ways to calculate mobile phones. 1. Pay a monthly rent of 22 yuan per month, and then charge 0.2 yuan per minute. 2. No monthly rent, 0.4 yuan per minute Q: if you talk for 80 minutes a month, which is cheaper?